<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>Document</title>
	<style>
		body{
			background: blue url() 0 0 no-repeat;
		}
		.box{
			width: 200px;
			height: 200px;
			/*background: red;
			background: #A349A4;
			background: rgb(13,56,45);*/
			background: rgba(237,38,36,0.5);
			/*用一个颜色来背景*/
		}

	</style>
</head>
<body>
	<div class="box">
		
	</div>
</body>
</html>